<!DOCTYPE html>
<html>
<head>
	<title></title>
    <meta charset="utf-8">

    <style type="text/css">

     ul{
     	list-style: none;
     	padding: 0;
     }
     .nav>li{
       float: right;
       margin-right:100px; 
     }

     .nav ul{
     	display: none;
     	position: absolute;
     	margin-left:-25px;  
     }

     .nav>li:hover>ul{
     	display: block;
     }




    
    </style>

</head>
<body>

  <ul class="nav">
     <li>首页
         <ul>
         	<li>第二级菜单</li>
         	<li>第二级菜单</li>
         	<li>第二级菜单</li>
         </ul>
     </li>
     <li>社会</li>
     <li>娱乐</li>
  </ul>

</body>
</html>